The present invention relates to a method for the manufacture of a flanged member for a pipe system and to a flanged member intended for use in a pipe system.
It has been known for a long time to join various parts and components for pressure equipment, especially in pipe systems, by using flanged members, usually called flanged pipe joints. By flanged member, also named flange member or merely flange, is here intended a pipe element having a ring-shaped collar or flange at one of its ends. So-called flanged pipe joints include two flanged members that are bolted together, and they are used, for instance, for the joining of pipes in numerous applications. A flanged member is then attached to one end of a pipe, usually by welding. Also an opposite piece of pipe is provided with a flanged member, and the flanged pipe joint is achieved by bolting those two flanged members together. Flanged members are also used for the connection of a piece of pipe to different components included in a pipe system, as for instance valves, a Y-piece or just another piece of pipe. In such a case a flanged member is attached to the free end of the pipe and then bolted to a corresponding and for this purpose adapted part of the valve. Also, other types of joint arrangements may be used, for instance joints of clamp or hoop type.
Flanged joints and other joints, where flanged members are incorporated, are used in numerous applications. It follows, that the actual dimensions of these pipes and flanged members may vary substantially. Regarding large size pipe, as for an example with applications within the offshore-, subsea-, process- and petroleum-industries and also in nuclear power plants, flanged joints and flanged members of traditional design, are characterised by considerable weight, large bulk and high cost. However, a special type of flanged joint/flanged member is known, a so called compact flange system, in which certain dimensioning principles are applied such that the flanges can be made substantially smaller than by using conventional design. The invention in the present case is particularly well suited for this type of compact flanges, although it is not limited to such.
As the flanged member normally is very bulky and consequently is a much more expensive component than a straight piece of pipe, an effort is usually made to make the flanged member as short as possible, in order to limit the need for space and the cost of material. In practice this means that its non-flanged end is made as short as possible. In cases with pipes having a relatively large outside diameter and consequently a large flange diameter, and at the same time a comparatively small wall-thickness, it will occur, during welding of the non-flanged end of the flanged member to a pipe element in the pipe system, such high heat transfer in the flanged member that the contact surface of the flanged end of the flanged member becomes deformed and warped. This problem is also common with small size flanges, having a rather small mass relative to the pipe shaped part of the flange member, and which therefore heat up rapidly. It is readily understood, that this circumstance does impair the performance of the joint tightness, which in many applications creates a most serious problem. Even a defect in the tightness that results in a very small leakage may, for instance, create a serious peril in cases when substances, which may endanger the environment, are transported in the pipe system.